ABSTRACT The Videofluoroscopic Swallow Study (VFSS) is the primary diagnostic test used to identify abnormalities in oropharyngeal swallowing function, detect the presence and etiology of aspiration, and test the effects of diet modifications and therapeutic interventions. While VFSSs are important diagnostic tests, they expose patients to ionizing radiation, which should be kept ?as low as reasonably achievable? due to the associated cancer risks. We currently do not know the excess cancer risks associated with this diagnostic test in children. This lack of knowledge is the cause of variable / erroneous clinical practice patterns ranging from not using this valuable exam to acquire important diagnostic information to using the exam but in a diminished manner (with reduced diagnostic accuracy) or potentially overusing the exam and possibly greatly increasing cancer risks. It is imperative that we understand the cancer risks so that clinicians, hospital safety boards, patients and caregivers can make informed decisions about the use of the Videofluoroscopic Swallow Studies in children. Due to concerns regarding radiation exposure and associated cancer risks, using an x-ray beam pulse rate (pps) of 15pps or a lower has become a widespread practice pattern despite the high likelihood that this compromises diagnostic accuracy, exposing patients to radiation and increasing cancer risks without providing useful diagnostic information. We found that, in adults, decreasing the pulse rate from 30 to 15pps significantly reduced diagnostic accuracy and changed treatment strategies. A young child's swallow occurs in about a third of the time of an adult swallow. When a reduced pulse rate of 15pps is used for a young child's VFSS, the diagnostic accuracy would be less than that of an adult's VFSS performed at 7.5pps, a rate that we know substantially decreases diagnostic accuracy. Despite this expected reduction in diagnostic accuracy, approximately 47% of hospitals use pulse rates of 15pps or lower to decrease children's radiation exposure. Clear evidence of the impact of using a pulse rate of 15pps or lower on diagnostic accuracy is needed to convince clinicians to change their practice. The information gained from the proposed experiments is desperately needed to guide the use of VFSSs in children, including the timing of and use of repeat VFSSs, and to facilitate accurate counseling of caregivers regarding the risks of the test. Once we know the radiation-related cancer risks for children from VFSSs, we can evaluate whether the benefit of reducing radiation exposure by using pulse rates of 15pps or less outweighs the risk associated with reduced diagnostic accuracy. Thus, the specific aims of this proposal are: Aim 1. Establish the standard radiation doses from VFSSs in children. Aim 2. Quantify patient cancer risks from VFSSs in children. Aim 3. Determine the impact of pulse rate on the assessment of swallowing impairment severity and treatment recommendations in bottle-fed children.